Fuzz FaceThis is the Fuzz Face, the legendary fuzz distortion pedal. With this PCB you can build the original or many other variants using either Germanium or Silicon transistors.
Designators and components Step 2 of 4
PCB FUZZ FACE DIY PCB GUITAR EFFECT
C1 2.2u 2.2UF 35V 105C RADIAL ELECTROLYTIC CAPACITOR 5X11MM
C2 22u 22UF 50V 105C RADIAL ELECTROLYTIC CAPACITOR 5X11MM
C3 10n 10NF 0.01UF 100V 5% POLYESTER FILM BOX TYPE CAPACITOR
C4 47u 47UF 25V 105C RADIAL ELECTROLYTIC CAPACITOR 5X11MM NICHICON
Q1 PNP 2N3906 / NPN 2N3904, BC108 or BC109
Q2 PNP 2N3906 / NPN 2N3904, BC108 or BC109
Sockets 40 PIN DIP SIP IC SOCKETS ADAPTOR SOLDER TYPE
R1 100k 100K OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
R2 33k 33K OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
R3 470 470 OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
R4 1M 100K OHM 1/4W 1% METAL FILM RESISTOR ROYAL OHM TOP QUALITY
Bias 50k 50K OHM TRIMMER POTENTIOMETER CERMET 1 TURN 3362P
FUZZ 1k-B 1K OHM LINEAR TAPER POTENTIOMETER
VOL 500k-A 500K OHM LOGARITHMIC TAPER POTENTIOMETER
NEGATIVE OR POSITIVE GROUND
The PCB is designed for the original positive ground version (PNP transistors). A positive ground pedal cannot be connected to the power supply in chain with your other pedals (negative ground). It is necessary to use a 9V battery, an isolated power supply or a voltage inverter.
If you are planning to use germanium transistors, you should build the positive ground version since most of the germanium transistors are PNP (for example AC128). However, if you are going to use silicon transistors, you should build the NPN version... which will be more convenient to power up the circuit in chain with your other pedals.
The original Fuzz Face uses germanium PNP transistors (AC128 or NKT275); You should use a low gain for Q1 (β=70-80) and a high gain for Q2 (β=110-130). Germanium transistors tend to have leakage current and a varying gain value. For the PNP silicon version, you can use 2N3906.
For NPN silicon version you can use 2N3904, BC108 or BC109. You can use sockets and try different transistor combinations. To use to the negative ground version (NPN transistors): change to NPN transistors, flip the polarity of the electrolytic capacitors (C1, C2 and C4) and connect the +9V where it is marked -9V.
Capacitors for PNP version Capacitors for NPN version
For the correct position of the transistors, you can use the following figures.
In the following table find some transistors you can use.
It is recommended to use sockets for the transistors. You can use 3 pin headers (40 PIN DIP SIP IC SOCKETS ADAPTOR SOLDER TYPE) or transistor sockets.
BIASING THE CIRCUIT
Place the trimmer to bias the circuit. By using a voltmeter, you can measure the voltage over the "Bias" pad and adjust to half of the power supply. For example, if you are using a 9V power supply, the bias voltage should be 4.5V. Note that if you are using germanium transistors the biasing will be influenced by ambient conditions such as temperature. Other method is just using your ears, rotate the trimmer until you find the point you most like.